SPECIAL REPORT | HYDROGEN
V That figure is likely an underestimate: dedicated plant may be used, but also electrolysers are likely to be used intermittently, at times when there is excess generation – raising the overall capacity requirement. But both methane reforming and electrolysis place other demands on the system – for heat, gas and, crucially, water. A ‘whole system’ view reveals some of the benefits, and also the complexity, of combining nuclear and hydrogen infrastructure. Heat, natural gas and water are key inputs, and when
it comes to outputs it is not enough to simply produce hydrogen; it must also be delivered to its users. How does the nuclear-hydrogen nexus fit together in
practice? Great Britain is an interesting test bed for this discussion,
as there is political support for both a fleet of new reactors and a switch to hydrogen to decarbonise industry and transport. It has announced an ambition for a dozen new reactors and it has provided research and development funding for hydrogen production and use. These are focused on several existing ‘industrial clusters’ in coastal areas. Finally, GB is a relatively small area (and for this purpose Scotland, which has outlawed new nuclear, can be excluded) so potential sites are relatively close together
situated tens rather than hundreds of miles apart. Although electricity can obviously be transported across country to power electrolysers, nuclear’s key heat offering (see below) cannot be transported in the same way. Even for electricity, limited grid capacity is already causing huge constraint costs and building new network is a slow and costly process. That means siting issues are make or break for nuclear’s role as a hydrogen producer. Sizewell, on the southern east coast, is a useful example,
as development consent was recently granted for a new reactor, Sizewell C, at the site. EDF has previously signalled hydrogen as a potential by-product at Sizewell C.
Heating up on hydrogen Beyond electrical power, nuclear’s ability to generate even larger quantities of heat also offers an opportunity in hydrogen production. Heat is crucial for steam methane reforming, as the name implies. In current deployment the heat is supplied using additional gas to create steam. That has the benefit of simplicity but it increases gas consumption by up to a third so alternate heat sources that don’t use fossil fuels are attractive. But it is electrolysis where the availability of high
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1 Anglian Water 2 Bournemouth and West Hampshire Water 3 Bristol Water 4 Cambridge Water 5 Essex and Suffolk Water 6 Folkestone and Dover Water 7 Mid Kent Water 8 Northumbrian Water 9 Portsmouth Water 10 Severn Trent Water 11 South East Water 12 South Staffordshire Water 13 South West Water 14 Southern Water 15 Sutton and East Surrey Water 16 Tendering Hundred Water 17 Thames Water 18 Three Valleys Water 19 United Utilities 20 Wessex Water 21 Yorkshire Water 22 Anglian Water (formerly Hartlepool Water)
temperature steam is a game-changer. Increasing the temperature at which electrolysis takes place increases the process efficiency significantly – from around 40% at 100°C to around 60% efficiency at 850°C. The still higher temperatures available from nuclear offer another option: high temperature steam electrolysis, which splits hydrogen and oxygen out from steam instead of water at temperatures towards 100°C, increasing hydrogen production efficiency to around the 80% level. Using electricity from nuclear to produce hydrogen is
relatively flexible on siting as it can be transmitted across country. Using nuclear’s heat is the opposite: practically, it cannot be transported long distances.
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Water stresses Currently, according to PA Consulting, for the two dominant electrolysers commercially available (alkaline and proton electron membrane technologies) water use is 9-14 kg per kg of hydrogen produced (depending on the amount of demineralisation required), with some estimates as high as 18 kg per kg. Methane reforming requires 6-13 kg of water per kg of hydrogen produced. To put it another way, a typical estimate is that when working consistently a 1 MW electrolyser will produce around 400 kg of hydrogen per day. That suggests water use of 3.6-5.2 cubic meters per day. Indeed, at Sizewell, EDF’s enthusiasm for hydrogen has
cooled because of potential problems in meeting the water demand at the site. At 800 cubic metres per day Sizewell B’s fresh water
requirement is dwarfed by its seawater demand (50 cubic metres a second) but it still represents about 7% of clean water demand in the local catchment area alone. Sizewell C will have a larger fresh water demand of around 2000 cubic metres per day. Despite GB’s rainy reputation, the east and south of
Above: UK water stress map reveals potential problems for hydrogen production 42 | September 2022 |
www.neimagazine.com
the country are referred to as ‘water stressed’ areas by environmental regulator the Environment Agency. To meet Sizewell C’s fresh water needs EDF had planned to install a pipeline to abstract water from the River Waveney, 18km away. However, the local water company, Essex and Suffolk Water anticipates that the area will be in “water
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